The raw and the cooked, caveman redux

A few months ago, Henry et al. (2011a) published a truly remarkable study that analyzed the phytoliths and starch grains that had gotten encrusted in the dental calculus (i.e., plaque) of three Neanderthal individuals, two from the site of Spy (Belgium), and another from the site of Shanidar (Iraq). Their study provided the first direct evidence that plant foods were an integral part of the Neanderthal diet by identifying phytoliths (the microscopic silicate 'skeletons' of plant parts that are unique to each plant species) of date palms in the calculus of Shanidar III, and starch grains attributed to various species of wild barley and legumes. The Spy I and II specimens yielded no phytoliths, but did yield starch grains that indicate they consumed water lily corms as well as some variety of sorghum and five other types of plants. The fact that these plant microfossils were found on the teeth of both Spy specimens is a strong indicator that these plants were part of the diet of that group as a whole, too. And the fact that Neanderthals from such distinct ecological settings preserve direct evidence of plant consumption suggests that it was a widespread dietary behavior, an observation that contrasts markedly with the 'Neanderthals as super-carnivore' idea that's been growing in the literature.

As if that wasn't enough, however, some of the starch grains found in the calculus of Shanidar III also had a peculiar morphology ("partly gelatinized") that matched that of experimental cooked barley starch grains. Further, Henry et al. (2011:487) observe that "The overall pattern of damage to the starch grains matches most closely with that caused by heating in the presence of water, such as during baking or boiling, rather than “dryer” forms of cooking like parching or popping (38). The finding of cooked Triticeae [barley] starches on the Shanidar teeth reinforces evidence from other studies that suggest that Near Eastern Neanderthals cooked plant foods." In other words, not only can we tell that Neanderthals cooked some of the plants they consumed, we can even get an idea of how they cooked them, most likely through boiling or baking. To me, this is doubly (triply?) neat because it also tells us something about the cooking technology this very likely required, namely some kind of cooking vessel, made out of either leather or wood.

However, Collins and Copeland (2011) now have a letter in press at PNAS that argues that Henry et al. (2011a) did not properly account for alternative manners in which starch grains can become partly gelatinized through various forms of diagenesis, that is post-depositional chemical or physical alteration, or what we commonly think of as decomposition. This diagenesis could have been triggered by both the presence of water in the cave sediments and/or their exposure to high heat.

I'm happy that PNAS actually gave Henry et al. (2011b) a chance to respond to this letter at the same time. In their reply, they point out, first,  that the heat and humidity required to prompt 'spontaneous' gelatinization would be extremely unlikely to be present in cave sediment. They also indicate that complementary analyses of starch grains on stone tools from some of the same contexts from which teeth associated with altered starch grains are not altered, in contrast to what would be expected if these processes were affecting whole archaeological layers. Specifically, it suggests that lithics were used to process uncooked plant matter that was then cooked and later consumed by Neanderthals. Overall, the evidence therefore continues to indicate that Neanderthals not only ate plants, but also cooked them to both facilitate their consumption and increase their nutritiousness.

References

Collins, M., & Copeland, L. (2011). Ancient starch: Cooked or just old? Proceedings of the National Academy of Sciences DOI: 10.1073/pnas.1103241108

Henry, A., Brooks, A., & Piperno, D. (2010). Microfossils in calculus demonstrate consumption of plants and cooked foods in Neanderthal diets (Shanidar III, Iraq; Spy I and II, Belgium) Proceedings of the National Academy of Sciences, 108 (2), 486-491 DOI: 10.1073/pnas.1016868108

Henry, A., Brooks, A., & Piperno, D. (2011). Reply to Collins and Copeland: Spontaneous gelatinization not supported by evidence Proceedings of the National Academy of Sciences DOI: 10.1073/pnas.1104199108